Question

PLZ HELP. A 75 kg astronaut floating in space throws a 5 kg rock at 5 m/sec. How fast does the astronaut move backwards

Answer 1

use conservation of momentum

Answer 2

Sit in an office chair and try to rotate without touching the ground. You'll notice you can wiggle in one direction and then you'll wiggle right back. This is conservation of momentum, and it's a totally real thing that you can experience with out even standing up.

Answer 3

Or do what I do when I go shopping and stand in a shopping cart and just try to move it. It's pretty hard (until you realize you can exploit static vs kinetic friction).